1. Field of the Invention
THIS INVENTION relates to a vehicle seat suspension unit. The term "vehicle" shall be used to include automobiles, four-wheel-drives (4WD), trucks, prime movers, earthmoving machines (e.g. bulldozers), aircraft and watercraft.
2. Prior Art
A vehicle operator's comfort and efficiency is dependent on providing a suitable suspension unit for his seat to eliminate, or at least reduce, the shocks and vibration transmitted from the vehicle to the operator via his seat.
Many suspension units have been proposed to reduce the shocks and vibration. Generally, most rely on a spring-loaded seat support frame which is damped by a hydraulic or pneumatic damper unit An example is disclosed in AU-B-66509/86 (582031) (D. M. Culley et al). The major problem with these units is that the damping can effectively be so slow that the suspension unit goes out of phase with the vehicle suspension and the damping can apply an additive shock to the operator's seat. In many cases, operators remove the damping effect as it is preferable to have a "floating" undamped suspension unit than a poorly damped one.
One of the reasons for the failure of the existing suspension units has been a basic misunderstanding of seat suspension unit design. The design objective is to provide a unit where the operator's seat follows an almost undisturbed path as the vehicle passes over bumps or depressions. In the past, the designers have worked on the principle of the seat moving relative to the vehicle, whereas they could have been designing for movement of the vehicle relative to the seat. In addition, they have applied damping to the suspension unit which is not required.